for your car...i would say no more than 2 inches...going wider doesnt mean more performance..and actually beyond a certain point...it will slow you down.

and you have an HKS muffler or a full exhaust system? Authentic HKS systems can last as long as 7-8 years...how old is yours?

I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it..and so restriction of free thought and free speech is the most dangerous of all subversions.